I bought a Vox Tonelab that uses a 12ax7 tube (valve) for the output but it uses the 12ax7 not as a preamp stage but as a power amp stage.
I changed the tube it came with for an old English tube I had that came from an old Marshall and it improved the sound a fair bit.
I've only used it for a while with a Strat and here are some of the presets that impressed me.
The Police preset which sounds very tubey and very like Andy Summers.
The Brian May preset sounds really close to Brian May and when I went through some Killer Queen riffs it was scary how close it was.
The Nashville preset sounds great for chickin pickin.
I played the Cars Best Friends Girl solo and it sounded great.
The Sabbath preset sounds like ummmm Tony Iommi and is pretty good.
The Unchained preset is pretty good for the later EVH sound.
Some of the other presets are a bit stupid and some sound bad but you can adjust things to tweak the sound like models and cabinets and effects and tone.
All in all the Vox Tonelab's a very useful thing to have and does have a tube like sound to it.

No it hasn't got USB but it has got a digital SPDIF out that can go straight into a soundcard.
I got it used and it comes with a manual with a section about computer recording and it's also got software and midi control.
My one is just the Tonelab with no controller pedals then after that came the Tonelab SE which I think has 2 controller pedals and then the Tonelab LE which has one controller pedal.

Np...I've got a Zoom G.2 and about four weeks after I bought it they released the G.2u with USB ..I love the pedal but regret not being able to record my models.
Sooooo...I've been watching the prices of Stienberger's STEALTH PLUG drop drastically...they were $199 when they were released...they've now dropped to $99.
Comes with CubaseLE and Amplitude.
Definately got my eye on one of those.

Maybe a Zoom G7.1UT is the best one with USB and a 12ax7 Tube/Valve.
I don't know how it sounds as I've never used Zoom stuff.
Some of the other things I've used are a Behringer V-Amp Pro which is pretty good for old Marshall sounds and high gain metal but the clean sounds are a bit brittle, A DigiTech RP-50 which is pretty basic but the Marshall sim is not too bad, Vox Tonelab which has the best clean sounds I've heard and a very tube like sound plus it's pretty good on 70's/80's rock as well with a very tube amp sound, Amplitube 2 which sounds pretty good to me but doesn't have the Vox Tonelabs tube sound.

Maybe a Zoom G7.1UT is the best one with USB and a 12ax7 Tube/Valve.
I don't know how it sounds as I've never used Zoom stuff.

I can't rave enough about Zoom..!!!
Apparently they had a bad rep at one stage about their overdrive modelling not sounding too good in the ME series of pedals but they've switched to another chip and it's sheer brilliance.
I have two overdrive models that I use patched side by side...a SRV type model for when I use my strat and a full on Gary Moore type of saturation for the LP.
The modulation effects are very useable...the autowah is pretty good as is the octave and doubling effects.